Test if save method is hit in unit test - asp.net-mvc

Question

I'm starting with unit testing in the asp.net mvc 4 framework.
I got a repository with basic crud methods and a save method. When I create a unit test I create a test repository and test if e.g. a item to the collection is added. That all goes smoothly but I cannot test if the save method is hit.
I tried to add a boolean property to the test repository which will be set to true if .save() is hit. But then I need to change the interface, and also the database repository. Which is in my opinion neither practical nor best practice.
What is the best method to test this? Thank you in advance for your answer.
My code:
the fake repository:
public class TestUserRepository : IUserManagementRepository
{
/// <summary>
/// entries used used for testing
/// </summary>
private List<User> _entities;
/// <summary>
/// constructor
/// </summary>
public TestUserRepository()
{
_entities = new List<User>();
_entities.Add(new User
{
Id = 1,
InsertDate = DateTime.Now,
LastUpdate = DateTime.Now,
Username = "TestUserName",
Password = "TestPassword"
});
}
...
public void Create(User task)
{
_entities.Add(task);
}
public void Save()
{
//do nothing
}
}
the controller to test:
[HttpPost]
public ActionResult Create(User user)
{
if (ModelState.IsValid)
{
_repository.Create(user);
_repository.Save();
return RedirectToAction("Index");
}
else
{
return View(user);
}
}
and the test
[TestMethod()]
public void CreateTest()
{
IUserManagementRepository repository = new TestUserRepository();
UserController controller = new UserController(repository);
User user = new User { Username = "UnitTestUserName", InsertDate = DateTime.Now, LastUpdate = DateTime.Now, Password = "Password" };
ActionResult actionResult = controller.Create(user);
User returnedUser = repository.FindBy(u => u.Username == "UnitTestUserName").First<User>();
Assert.IsNotNull(actionResult);
Assert.AreEqual(user, returnedUser);
}

Answer 1

You must be careful not to write a bunch of unit tests that just test your test repository.
Consider the following scenario:
You have a service method, that is supposed to add an item to your repository.
Your unit test calls this method, and you should verify that the appropriate "AddX" method was called on the repository.
This is a valid unit test scenario, to test it you can use your test repository. Since it is your test object, you have full control over it. You can expose properties such as "AddXMethodCallCount" or something similar.
Over time you will find yourself writing a lot of test code that is pretty much boilerplate. The alternative, which I strongly recommend, is to use a mocking framework:
https://stackoverflow.com/questions/37359/what-c-sharp-mocking-framework-to-use
It takes some getting used to, but once you get it, it will speed up your unit testing significantly.
If you don't want to use mocking yet, but want to still achieve your goal of verifying whether or not Save() is called, I would suggest just adding a publicly exposed SaveMethodCallCount property:
public class TestUserRepository : IUserManagementRepository
{
...
public SaveMethodCallCount {get; set;}
...
public void Save()
{
SaveMethodCallCount++;
}
}
This works, because in your unit test you can actually say:
TestUserRepository repository = new TestUserRepository();
The UserController does not care, as long as the passed in parameter implements the IUserManagementRepository interface. The controller interacts with the repository object through the interface, but the unit test does not have to, and the TestUserRepository, being a test class, is allowed to have much more functionality, that does not have to be exposed through the interface.
So your test could look something like:
[TestMethod()]
public void CreateTest()
{
TestUserRepository repository = new TestUserRepository();
UserController controller = new UserController(repository);
User user = new User { Username = "UnitTestUserName", InsertDate = DateTime.Now, LastUpdate = DateTime.Now, Password = "Password" };
ActionResult actionResult = controller.Create(user);
User returnedUser = repository.FindBy(u => u.Username == "UnitTestUserName").First<User>();
Assert.IsNotNull(actionResult);
Assert.AreEqual(user, returnedUser);
Assert.AreEqual(1, repository.SaveMethodCallCount);
}
To make my example complete, let me show you what this would look like if you used a mocking framework, like Moq. You can see some more examples here. The example test method uses Moq and Arrange/Act/Assert, and tests only one thing - that Save() is called when Create() is called.
[TestMethod()]
public void Test_SaveCalledWhenCreateCalled()
{
// Arrange
// First, instead of creating an instance of your test class, you create a mock repository.
// In fact, you don't need to write any code, the mocking framework handles it.
var mockRepository = new Mock<IUserManagementRepository>();
// and pass the mock repository (which implements the IUserManagementRepository) to your controller
UserController controller = new UserController(mockRepository);
// Act
ActionResult actionResult = controller.Create(user);
// Assert
// see how easy it is to do with a mocking framework:
mockRepository.Verify(rep => rep.Save(), Times.AtLeastOnce());
}